Unless otherwise indicated herein, the description provided in this section is not itself prior art to the claims and is not admitted to be prior art by inclusion in this section.
A typical cellular wireless network includes a number of base stations each radiating to define a respective coverage area in which user equipment devices (UEs) such as cell phones, tablet computers, tracking devices, embedded wireless modules, and other wirelessly equipped communication devices, can operate. In particular, each coverage area may operate on one or more carriers each defining a respective frequency bandwidth of coverage. In turn, each base station may be coupled with network infrastructure that provides connectivity with one or more transport networks, such as the public switched telephone network (PSTN) and/or the Internet for instance. With this arrangement, a UE within coverage of the network may engage in air interface communication with a base station and may thereby communicate via the base station with various remote network entities or with other UEs served by the base station.
Further, a cellular wireless network may operate in accordance with a particular air interface protocol (radio access technology), with communications from the base stations to UEs defining a downlink or forward link and communications from the UEs to the base stations defining an uplink or reverse link. Examples of existing air interface protocols include, without limitation, Orthogonal Frequency Division Multiple Access (OFDMA (e.g., Long Term Evolution (LTE) and Wireless Interoperability for Microwave Access (WiMAX)), Code Division Multiple Access (CDMA) (e.g., 1×RTT and 1×EV-DO), and Global System for Mobile Communications (GSM), among others. Each protocol may define its own procedures for registration of UEs, initiation of communications, handover between coverage areas, and other functions related to air interface communication.
In practice, base stations in a cellular wireless network can be physically arranged in various ways. For instance, base stations may be co-located with each other by having their antenna structures at largely the same geographic location (within a defined tolerance, for instance). By way of example, a single cell site could be arranged to define two base stations with separate antenna structures on a common antenna tower or other base structure. And in another example, a single physical base station (possibly with a single antenna structure) that provides service separately on first and second carriers could be considered to define the two separate base stations, one operating on the first carrier and the other operating on the second carrier. Alternatively, base stations in a cellular wireless network can be distributed at some distance from each other. In particular, the antenna structure of a given base station may be located at a geographic location that is at some non-zero distance from the antenna structure of another base station.
With these arrangements, the base stations of a wireless service provider's network would ideally provide seamless coverage throughout a market area, so that UEs being served by the system could move from coverage area to coverage area without losing connectivity. In practice, however, it may not be possible to operate a sufficient number of base stations or to position the base stations in locations necessary to provide seamless coverage. As a result, there may be holes in coverage.
One way to help to resolve this problem is to operate a relay node (RN) that extends the range of a base station's coverage area so as to partially or completely fill a coverage hole. Such an RN may be configured with a wireless backhaul interface for communicating with and being served by the base station in much the same way that a UE does, and a wireless access interface for communicating with and serving one or more UEs in much the same way that a base station does. Further, the RN may include control logic for actively bridging the backhaul communications with the access communications. The RN may thus receive and recover downlink communications from the donor base station and may transmit those communications to the UEs served by the RN, and may likewise receive and recover uplink communications from UEs served by the RN and may transmit those communications to the base station.
In this arrangement, the base station is considered to be a “donor base station,” in that the base station provides coverage to the RN and the RN then provides coverage to one or more UEs. In practice, the wireless communication link between the donor base station and the RN is considered to be a “relay backhaul link,” and the wireless communication link between the RN and UEs served by the RN is considered to be a “relay access link.” Further, to the extent the base donor station itself also serves UEs, the wireless communication link between the donor base station and those UEs is considered to be a “donor access link.”
Advantageously, an RN like this might have a relatively small form factor, with antenna height lower than the base station and with reduced transmit power requirements and cost. Consequently, a wireless service provider may conveniently employ such RNs throughout a region to help efficiently fill coverage holes and improve service quality.